Modern mobile communication tends to be more to provide multimedia services with high-speed transmission. FIG. 1 is a schematic diagram illustrating a structure for a system of system architecture evolution (SAE).
A user equipment (UE) 101 is a terminal device used to receive data. An evolved universal terrestrial radio access network (E-UTRAN) 102 is a wireless access network, which includes a macro base station (eNodeB/NodeB) providing an interface for the UE to access the wireless network. A mobility management entity (MME) 103 is responsible for managing mobility context, session context and security information of the UE. A service gateway (SGW) mainly provides a user-plane function. The MME 103 and the SGW 104 may be deployed in a same physical entity. A packet data network gateway (PGW) 105 is responsible for functions such as charging, lawful monitoring and so on, also may be deployed in a same physical entity with the SGW 104. A policy and charging rule functional entity (PCRF) 106 provides a principle of quality of service (QoS) and a charging rule. A Serving GPRS Support Node (SGSN) 108 is a network node device, which provides routing for data transmission in Universal Mobile Telecommunications System (UMTS). A Home Subscriber Server (HSS) 109 is a home sub-system of the UE, which is responsible for protecting user information such as a current position, an address of a service node, user security information, packet data context of the user equipment and so on.
A small cell enhancement requirement is provided in 3GPP Release 12 (Rel-12). As shown in FIG. 2, target scenarios of small cell enhancement include a scenario with macro cell coverage and a scenario without the macro cell coverage, an indoor scenario and an outdoor scenario, a scenario with an ideal backhaul and a scenario with a non-ideal backhaul.
In a condition with the macro cell coverage, a carrier aggregation technology is provided, which is applied among different base stations. A macro cell and a small cell may work on different frequency bands. In a condition without the macro cell coverage, there is no a specific solution how to enhance small cell performance.